In general, a liquid ejection head which ejects ink is mounted on an ink jet recording apparatus which records an image on a recording medium by ejecting ink thereto. As a mechanism which causes the liquid ejection head to eject ink, there is a known mechanism which uses a pressure chamber of which the volume can be shrunk by a piezoelectric element. In this mechanism, when the pressure chamber is shrunk by the deformation of the piezoelectric element to which a voltage is applied, the ink inside the pressure chamber is ejected from an ejection orifice which is formed in one end of the pressure chamber. As a liquid ejection head with such a mechanism, there is known a so-called shear mode type in which one or two inner wall surfaces of a pressure chamber are formed of a piezoelectric element and the pressure chamber is contracted by shearing the piezoelectric element through the application of a voltage thereto.
In an ink jet apparatus for industrial purpose, there is a demand for the use of a highly viscous liquid. In order to eject the highly viscous liquid, the liquid ejection head needs to have a larger ejection force. In order to meet such a demand, there is proposed a liquid ejection head which is called a so-called gourd type in which a pressure chamber is formed of a cylindrical piezoelectric member with a circular or rectangular cross-sectional shape. In the gourd type liquid ejection head, the pressure chamber can be expanded or contracted in such a manner that the piezoelectric member is uniformly deformed with respect to the center of the pressure chamber in the inward-outward direction (the radial direction). In the gourd type liquid ejection head, since all wall surfaces of the pressure chamber are deformed and the deformation contributes to the force of ejecting ink, it is possible to obtain a larger liquid ejecting force compared to the shear mode type in which one or two wall surfaces are formed of the piezoelectric element.
In the gourd type liquid ejection head, there is a need to arrange plural ejection orifices with higher density in order to obtain higher resolution. With such arrangement, there is a need to arrange the pressure chambers respectively corresponding to the ejection orifices with higher density. PTL 1 discloses a method of manufacturing a new gourd type liquid ejection head in which pressure chambers can be arranged with high density.
In the manufacturing method disclosed in PTL 1, first, plural grooves which extend in the same direction are formed in each of plurality piezoelectric plates. Subsequently, the plural piezoelectric plates are stacked with the directions of the grooves matched, and are cut in the direction perpendicular to the directions of the grooves. In the cut piezoelectric plate, the groove portion forms the inner wall surface of the pressure chamber. Subsequently, in order to separate the respective pressure chambers, the piezoelectric member present between the pressure chambers is removed up to a predetermined depth. The upper and lower portions of the piezoelectric plate with the completed pressure chambers are connected to a supply path plate, an ink pool plate, a printed circuit board, and a nozzle plate, thereby completely manufacturing the liquid ejection head. According to the manufacturing method disclosed in PTL 1, since the pressure chambers can be arranged in a matrix shape, the pressure chambers can be arranged with high density. Further, according to this manufacturing method, since the groove can be easily processed in the piezoelectric plate compared to the case of perforating the piezoelectric plate, it is considered that the pressure chamber can be formed with high precision.
In the liquid ejection head which is manufactured by the manufacturing method disclosed in PTL 1, the plural pressure chambers are arranged with a space interposed therebetween. For this reason, in particular, when the length (the height) of the pressure chamber is made to be long in order to eject a highly viscous liquid (in order to increase the force of ejecting a liquid), the rigidity of the liquid ejection head reduces. When the rigidity reduces, a liquid may not be ejected when the pressure chamber is folded.